The present invention relates to a method of controlling a power train of an automotive vehicle. The term "power train" is used herein to mean a power generating and delivery system which includes an engine and a transmission.
The power train of this kind is used for example as a drive system of an automotive vehicle. Until recently, it has been the common practice in controlling the power train to control an engine in a discrete manner from controlling a transmission as reported for example in an SAE technical paper 830423 published by Society of Automotive Engineering (SAE). In controlling an engine, an engine controller detects data from various portions of the engine and adjusts a fuel supply, an ignition timing, an EGR flow rate and an intake air flow rate to optimal values resulting from computations on the detected data. In controlling a transmission, a transmission controller detects an engine load and a vehicle speed, and decides a gear position to be established in the transmission and performs a lock-up control based on the result of computations on the detected data. The engine controller is connected to the transmission controller such that operation data are communicated with each other thereby to restrain and control each other.
However, this conventional control method wherein the power train is controlled such that the engine and the transmission are controlled in the discrete manner by different controllers which operate in a discrete manner requires a very expensive control system consisting of a great number of components, causing a high failure probability and a disadvantage in weight. Besides, it is difficult to control the engine in synchronization with the control of the transmission. That is, the requirement of an action of a high priority level cannot cause an immediate initiation of the action required while a program is being executed and the execution of the action required cannot be initiated till the completion of the program under execution, thus rendering the overall control of the power train incorrect.